1. Field of Invention
The invention relates to an image processing technology, and more especially to a technology that can quickly and accurately find out an eye from a face image.
2. Related Prior Art
Technology related to eye state identification, such as detecting a driver's eye state to identify whether he/she is dozing off while driving, or detecting eye movement of a person suffering from Amyotrophic lateral sclerosis (ALS) for control purpose, has been widely known. Also, there are lots of patent applications, for example, Taiwan Patent No. 436436, I349214, M416161, TW 201140511, U.S. Pat. No. 8,094,883, U.S. Pat. No. 8,184,008, CN101196993 and so on, which describe an image processing method for eye state identification. The aforementioned technology comprises several steps, including capturing a user's face by a camera device to obtain images of the user's face, processing these images by an eye-identification device, and then determining the eye state of the user based on the processed results. The step of processing each of the images by the eye-identification device mentioned above further comprises the following sub-steps in sequence: finding out a face area, obtaining an eye area according to the face area that is found, attaining an specific area of the eye based on the eye area (such as upper eyelid, lower eyelid, or pupil), and determining the eye state of the user (i.e. whether the eye is opened or closed) according to variation of the specific area. However, how to find out the eye area on the face image quickly and precisely is one of the significant issues.
A conventional eye detection apparatus disclosed in China Patent No. 101196993 includes means for finding out positions of nostrils from a face image, means for establishing an eye searching area based on the positions of the nostrils, and means for attaining upper and lower eyelids from the eye searching area. It is understood that the nostrils on the face image is black, which therefore can be easily and precisely identified. Accordingly, in comparison with the traditional way to find out the eye directly from the face image, the eye detection apparatus can find out the eye more quickly and precisely.
Nevertheless, the eye searching area established by the conventional eye detection apparatus is a rectangle area with a horizontal side and a vertical side greater than the horizontal side, which covers a large area including eyebrows and cheeks. This obviously results another problems that the conventional eye detection apparatus would take much more time on finding out the upper/lower eyelids on the large eye searching area.